As a member of the 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, extraordinary metal‐like ductility, high plastic deformation strain, unique layered structure, and very low solubility has offered a platform for achieving tremendous success in various fields. Great achievements have been made in exploring the linear optical, mechanical, and photoelectric properties of 2D Ag2S nanosheets. However, the nonlinear optical properties of 2D Ag2S nanosheets and their applications in ultrafast photonics have not been studied. The saturable absorption property of 2D Ag2S nanosheets is experimentally illustrated at the telecommunication band with a large optical modulation depth of 15.5% and a low saturable intensity of 250.4 MW cm−2. Moreover, the 229th harmonic soliton molecule with repetition rate of 1.1 GHz based on 2D Ag2S saturable absorber is realized at the telecommunication band for the first time to the authors' knowledge. Thankfully, 2D Ag2S nanosheets display excellent nonlinear optical properties suggesting that this may open a new door for advanced photonic devices based on 2D Ag2S nanosheets.

Tin diselenide (SnSe2) nanosheets as novel 2D layered materials have excellent optical properties with many promising application prospects, such as photoelectric detectors, nonlinear optics, infrared photoelectric devices, and ultrafast photonics. Among them, ultrafast photonics has attracted much attention due to its enormous advantages; for instance, extremely fast pulse, strong peak power, and narrow bandwidth. In this work, SnSe2 nanosheets are fabricated by using solvothermal treatment, and the characteristics of SnSe2 are systemically investigated. In addition, the solution of SnSe2 nanosheets is successfully prepared as a fiber‐based saturable absorber by utilizing the evanescent field effect, which can bear a high pump power. 31st‐order subpicosecond harmonic mode locking is generated in an Er‐doped fiber laser, corresponding to the maximum repetition rate of 257.3 MHz and pulse duration of 887 fs. The results show that SnSe2 can be used as an excellent nonlinear photonic device in many fields, such as frequency comb, lasers, photodetectors, etc.

Metal−organic frameworks (MOF) or their derivatives have attracted much attention in recent years due to exciting properties such as high specific surface area, adjustable pore size, and easy functionalization, which makes them have unique advantages in the fields of catalysis, energy storage, optoelectronics, and so on. However, the study of them in the fields of nonlinear optics and ultrafast photonics is still in its early stage. Here, by annealing the MOF template, porous MOF-derived CuO octahedra are prepared and applied to the above fields. Experiments show that CuO octahedra possess an excellent nonlinear optical absorption capacity in the near-infrared band. When it is used as a saturable absorber (SA) to the fiber lasers, high order harmonic soliton molecules with a repetition frequency up to 238 MHz can be obtained that make sense for optical frequency combs and optical communication. Besides, the dynamic evolution of the harmonic soliton molecule is explored. This work pioneers the application of MOF-derived metal oxide polyhedra as SAs in fiber lasers and expands the application fields of MOF-based materials. Moreover, this kind of emerging microstructured polyhedral SA, prepared by the new method, provides researchers with a new choice beyond quantum dots, nanoparticles, and 2D nanosheets/nanofilms.

Stannic sulfide (SnS2), a latterly developed two-dimensional (2D) material, has fascinated scientists because it can be widely applied to materials chemistry, biomedicine, photocatalysis, and so on. Especially, SnS2 has the advantages of adjustable band gap and good oxidation resistance, which indicates that this material has promising potential in nonlinear optics. However, the light interaction with SnS2 is rarely investigated. In this study, high-quality SnS2 nanosheets (Ns) developed through a liquid phase exfoliation approach have been applied in ultrafast photonics for nonlinear processes. This fabrication approach can greatly increase the damage threshold of the SnS2 saturable absorber (SA). Furthermore, the SnS2 SA device is applied to an erbium-doped fiber laser (EDFL) to obtain soliton molecules with different orders. Ultimately, eleventh-order soliton molecules, the highest order of soliton molecules through SnS2, are generated with a soliton separation of 8 ps and a spectral modulation period of around 1 nm. The above experimental results indicate that SnS2 has broad application prospects in the fields of mode-locked fiber laser and optical fiber communication.

Benzoxathiazine dioxide, as a bioisostere of the clinically widely used diazoxide, exhibits interesting biological activity. However, limited success has been achieved in terms of its concise and direct synthesis. We report herein a facile electrochemical migratory cyclization of N‐acylsulfonamides to access a diverse array of benzoxathiazine dioxides. The inclusion of electrochemistry is crucial for realizing such a novel transformation, which is substantiated both by the experiments and density‐functional‐theory calculations.